Apparatus for applying a surface coating of a liquid to a sheet

ABSTRACT

An apparatus for applying a surface coating of a liquid to a thin sheet passing through the apparatus includes a backing member having a projecting sheet abutting portion which urges the sheet against a movable brush, for example in the form of a rotating roller, which is immersed in the liquid. The projecting sheet abutting portion of the backing member deflects a part of the brushing portion of the brush away from the trailing edge of the sheet as the sheet passes downstream of the brush and thus prevents the trailing edge of the sheet from being distorted by the brush.

United States Patent Adams [4 1 Feb. 15, 1972 [54] APPARATUS FOR APPLYING A [56] References Cited SURFACE COATINGOF A LIQUID TO A UNITED STATES PATENTS SHEET 504,224 8/1893 7 Lappe ..l18/224 x [72] inventor: Ronald Allred Charles Adams, Kent, En- 718,527 "1903 l8/243 X gland v 128,193 6/1972 Weiss ..118/248 X #73] A B an h Limmd 771,544 10/1904 Goldsmith ..118/119 ssigneez owson p y Primary Examiner-John P. Mclntosh [22] 1970 Attorney-Sandoe, l-lopgood and Calimafde [21] Appl. No.: 4,673

[57] ABSTRACT [30] Foreign Applicat n Priority D1118 I An apparatus for applying a surface coating of a liquid to a thin sheet passing through the apparatus includes a backing Jan. 23, 1969 Great Britain ..4,028/69 member having a projecting sheet abutting portion which urges the sheet against a movable brush, for example in the [52] U.S. Cl. ..95/89 R, 15/77, 111188022264, form ofa rotating toner, which is immersed in the quhi The Int Cl Goad 5/06 projecting sheet abuttingportion of the backing member I 58] d 249 l 19 v deflects a part of the brushing portion of the brush away from the trailing edge of the sheet as the sheet passes downstream of the brush and thus prevents the trailing edge of the sheet 7 from being distorted by the brush.

7 10 Claims, 7 Drawing Figures msmmrsa 1s m 3.641.905

SHEET 1 UF 2 RONALD AL RED CHHRLES. mans INVBN'IOR J w w A TTO RNEYS APPARATUS FOR APPLYING A SURFACE (ZOATING- OF A LIQUID TO A SHEET This invention relates to an apparatus for applying a surface coating'of a liquid to a'sheet such as, for example, for applyinga surface coating of developer liquid to an imagewise exposed lithographicplate.

Ifv a lithographic printing plate processing apparatus, in.

whichaprocessingsolutionis applied to a first-surface of a lithographic plate passingthrough the apparatus: by one ormore rotating: brushes: having a brushing actionon the first surfacewhichis in the same direction as the movement of the ,or less pronounced bend in its trailing edge area. Such a distorted lithographic plate can present difficulties in subsequent handlingwhen it is being prepared for printing. Rota tion' of the brush or brushes at a peripheral speed which. is severaltimes greater than the linear speed'at which'thelithographic plate is drawn pastthe brushes, which is desirable soas to ensure that a good coating is. effected, is liable to aggravate any suchdistortion of: the trailing edge of the litho-- graphic plate.

According to the present invention there is. provided. a backing member in or for use in-an apparatus for applying a surface coating: of; a liquid to a sheet; which apparatus comprises a guide'means defining'a path for the sheetthrough'the apparatus and' movable brush means partially immersible in the-liquid andlocated adjacent the path for exerting a brushing action onthe sheet in the samedirection-as that inwhich the'sheetmoves along-said path, said backing member including? a projecting sheet abutting. means to urge the sheet into brushing relationship with the movable brush means and to deflect, away from the trailing edge of thesheet, a. part of the brushing portion of the movable brush means which is upstream of the trailing edge of the sheet during passage of the sheet downstream of the movable brush. means.

Preferably the backing member is such as to, allow the trail.-

ing-ed'ge of the sheet to be deflected away from the movable brush means by. another part of the brushing portion of the movable brush means as the trailing edge is passed downstream of the projecting sheet abutting means. In this case, the projecting sheet abutting means is so constructed and so disposed that it does not extend downstream of the brush means to any great extent so that it does. not restrictv deflection of'thesheet away from the brush means by said another'part of the brushing portion of the brush means.

The backing member may-comprise a backing plate, the sheet abuttingmeans projecting from the plate towards themovable brush means and extending transversely across the path of the sheet through the apparatus. The sheet abutting means may have various forms. For example, the sheet abutting means may be in the form of a rib normal to the backing plate, an inclined plate optionally being secured by one edge to that end of the rib most remote from the backing plate and by its opposite edge to a part of the backing plate downstream of the rib. Alternatively, the sheet abutting-means may comprise two oppositely inclined plates having first edges secured together and second edges, opposite to the first edges, secured to the backing plate, the points of attachment of the inclined plates to the backing plate being spaced apart in the direction in which the sheet moves through the apparatus. In a further embodiment, the sheet abutting means is in the form of an arcuate plate or rotatable roller, secured to the backing plate so that it is transversely arranged across the path of the sheet through the apparatus. That face of projecting sheet abutting means ofthe backing member, which holds a sheet passing through the machine in brushing contact with the brushing portion of the-brush means may be provided with a dimpled surface so as to reduce the area of the surface which actually contacts the sheet and thus to minimize the danger of the sheet sticking to the backing-member.

The apparatus may be provided with more than one movable brush-means,'each such brush means being associated with a projecting sheet abutting means of a backing member definingpart of the path along which the sheetsare guided through the apparatus. The brushing portion of the or each brush meansmay be of bristle. Alternatively brush means comprising-a suitable felt or sponge material may be used.

For a better understanding of the invention and to show how. the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which:

FIG. 1 is a side elevation of an apparatus of the invention,

FIGS. 2 and 3 are side elevations of a part of the apparatus of FIG. 1 on an increased scale and at different stages in the operation of the-apparatus,

FIG. 4 is a side elevation of one embodiment of a part of the apparatus of the invention,

FIG. 5 is aside elevation of another embodiment of the part shown in FIG. 4,

FIG. 6 is aside elevation of a further embodiment of the part shown in FIG. 4, and

FIG. 7 is a side elevation of yet a further embodiment of the part shown in FIG. 4.

Referring to FIGS. 1 to 3, there is shown an apparatus of the invention forprocessing imagewise exposed lithographic plates by applying to the surface thereof a developer liquid. The apparatus includes a pair of entry rollers l and 2 and a pair of exit rollers 3 and 4 which are adapted to pass each lithographic plate 5 along a path through the apparatus. The apparatus includes two rotatable cylindrical brushes 6 and 7 and the backing member 8, the brushes 6 and 7 and the backing member 8 defining a part of the path along which each lithographic plate 5 is passed by the entry and exit rollers. Each brush is mounted for rotation about its longitudinal axis which is disposed horizontally above the surface of developer liquid 9 contained in an open-topped tank 10. The liquid 9 is to be applied to the image wise exposed surface of the lithographic plate 5 by the apparatus. The radial dimension of each brush, that is to say the distance between the axis of rotation of the brush and the tip of the bristles of the brush, is greater tha n'the height of the axis above the surface of the liquid 9 and greater than the shortest distance between the axis and the backing member 8. The apparatus is provided with a suitable motor (not shown) for rotatably driving each brush about its axis of rotation so that the brush may exert a brushing action on each lithographic plate 5 passed along the path, the brushing action being in the same direction as that in which the lithographic plate moves along the path through the apparatus.

The backing member 8 comprises a rectangular backing plate 11 and two transverse ribs 12 and 13 which project from and are normal to a major surface of the backing late 11. The backing member is mounted within the apparatus with the backing plate 11 substantially horizontal and the transverse ribs positioned vertically above the axes of rotation of the brushes 6 and 7 and extending along the length of the brushes. That end face of each transverse rib most remote from the backing plate 11 serves to urge each lithographic plate 5 passing along its path through the apparatus into brushing contact with each brush by abutting against the reverse side of the lithographic plate. The thickness of each transverse rib is generally small compared to the radial dimensions of the brushes. The substantially horizontally disposed backing plate 11 is spaced from the axes of rotation of the brushes, by a distance which is substantially greater than the radial dimensions of the brushes.

In operation of the machine, eachlithographic plate 5 is in-. troduced into the machine via the entry rollers l and 2 and the. T

brushes are rotatably driven about their axes of rotation by the motor, the peripheral speed of the brushes being several times greater than the linear speed at which the plate 5 is'passed between the brushes and the end faces of the transverse ribs 12 and 13 of the backing member 8. As a result of the rotation of the brushes the bristles of the brushes emerge from the tank charged with the liquid 9 and the liquid charged bristles are then brought into good brushing contact with the lower surface of the lithographic plate 5 so that the liquid 9 is applied to that surface. i

As each lithographic plate passes along its path through the apparatus and the trailing edge 14 ofthe lithographic plate approaches each brush, the lithographic plate continues to be held in contact with the brush by the end face of the transverse rib associated therewith. This situation is shown in FIG. 2. when the trailing edge 14 has passed to the downstream side of the-rib (as shown in FIG. 3) so that the lithographic plate is no longer located between the end face of the rib and the brush, those bristles which are still upstream of the trailing edge willrotatetowards the rib and strike the rib. Only those bristles of the upper brushing portion of the brush on the downstream side of the rib will be in contact with the lithographic plate. Bristles which strike the rib are held back, bent as the brush rotates and prevented from straightening out by the rib. Further rotation of the brush continues to bend these bristles until their tips are drawn past the rib whereupon they tend to spring into their normal configuration. As the bristles return to their normal configuration the tips follow an upward path (denoted by the arrow 15 in FIG. 3) and, at normal speeds of rotation of the brush, these bristles will not have retained their normal configuration until they have been drawn through a substantial angular displacement with respect -to the rib. Thus, the bristles which contact the rib are deflected away from the trailing edge 14 of the lithographic plate so that they do not tend to impart a downward bending force thereupon. Moreover, the trailing edge 14 of the lithographic plate is pushed upwards out of the way of the bristles which have been drawn past the rib, the upward push being derived from those bristles which were in contact with the rearward portion of the lithographic plate as the trailing edge was drawn clear of the rib.

If desired, the exit rollers 3 and 4 may be arranged so as to lift the trailing edge of the sheet away from the brush means, or the last brush means, once the trailing edge of the sheet has passed downstream of the projecting sheet abutting means associated with that brush means.

Various alternative or modified forms of backing member may be employed in place of the backing member described above and examples of such other forms of backing member are shown in FIGS. 4 to 7.

Referring to FIG. 4, the backing member comprises a substantially rectangular backing plate 16 and a transverse rib 17 similar to one of the ribs 12 and 13 of the backing member of FIGS. 1 to 3. In addition, however, the backing member includes an inclined plate 18 which is located on the downstream side of the transverse rib l7 and which extends between the backing plate 16 and that end of the rib 17 most remote from the backing plate 16 to define an acute angle both with the rib 17 and the backing plate 16.

Referring to FIG. 5, the backing member comprises a backing plate 19 having planar surface adjacent and parallel to the path of the lithographic plates through the apparatus to which surface are secured two transverse oppositely inclined substantially rectangular plates 20 and 21. One edge of each of the plates 20 and 21 is secured to the planar surface of the plate 19 so that the points of attachment are spaced apart along the direction the lithographic plates move through the apparatus and the opposite edges of the plates 20 and 21 are joined together. Thus, inclined plate 20 defines a diverging element with respect to said backing plate 19, inclined plate 21 defines a converging element with respect to said backing platel9, and the join-between the plates 20 and 2l'serves as a lithographic plate abutting means to urge the lithographic plates into brushing relationship with the brush associated with the backing member.

Referring to FIG. 6, the backing member comprises a substantially rectangular backing plate 22 having'an arcuate longitudinal plate 23 of .semicylindrical form extending across the surface of the backing plate 22 with its longitudinal axis substantially perpendicular to the path of lithographic plates through the apparatus. The longitudinal edges'of the longitudinal plate 23 are secured to said surface and the arrangement is such that the path of the lithographic plates through the apparatus lies tangentially to the convex surface of the plate 23, which convex surface serves as a lithographic plate abutting means to urge the lithographic plates into brushing contact with the brush with which the member is associated.

Referring to FIG. 7, the backing member comprises a backing plate 24 having on its planar surface nearest the path of lithographic plates through the apparatus, brackets 25 in which is rotatably mounteda roller 26 extending across the surface of the backing plate 24. The arrangement is such that the path of lithographic plates through the apparatus lies tangentially to the roller which serves to urge the lithographic plates into brushing contact with the brush with which the member is associated.

Although the present invention as hereinabove specifically described is directed to apparatus for processing lithographic printing plates it will be appreciated that the invention is applicable to apparatus for applying a surface coating to other forms of thin sheeting. By the term thin sheeting there is to be understood sheeting having a thickness which is generally small compared with the length and breadth of the sheeting such that an end portion of the sheeting may be easily deformed by a bending force applied to it by rotating brushes.

What is claimed is:

1. An apparatus for applying a surface coating of a processing liquid to a lithographic plate, comprising a pair of entry rollers and a pair of exit rollers which guide and feed said lithographic plate along a path through the apparatus, rotatable brush means wetted by the processing liquid located beneath said path in position to brush the under face of said lithographic plate in the same direction as that in which said lithographic plate moves along said path, said lithographic plate being supported between said entry rollers and said exit rollers only by said brush means, and backing means located above said path and including a depending member extending transversely across said path and engaging the upper face of said lithographic plate to urge said lithographic plate into brushing relationship with said rotatable brush means and to engage and deflect, away from the trailing edge of the lithographic plate, a part of the brushing portion of said rotatable brush means which is upstream of the trailing edge of the lithographic plate during the passage of the lithographic plate downstream away from said rotatable brush means.

2. Apparatus as claimed in claim 1, wherein said backing means comprises a backing plate and the depending member projects from the backing plate towards the brush means.

3. An apparatus ascIaimed in claim 2, wherein the depending member comprises a rib normal to the backing plate.

4. An apparatus as claimed in claim 3, and further comprising an inclined plate having one edge secured to that end of the rib most remote from the backing plate and its opposite edge secured to a part of the backing plate downstream of the rib.

5. An apparatus as claimed in claim 2, wherein the depending member comprises two oppositely inclined plates having first edges secured together and second edges, opposite to said first edges, secured to the backing plate, the points of attachment of the inclined plates to the backing plate being spaced apart in the direction of said path.

6. An apparatus as claimed in claim 2, wherein the depending member comprises an arcuate plate secured to said backing plate.

than one cylindrical brush rotatable about an axis and more than one depending member, each cylindrical brush being associated with a depending member.

10. An apparatus as claimed in claim I, which includes more than one of the rotatable brush means and more than one depending member, each rotatable brush means being associated with a depending member. 

1. An apparatus for applying a surface coating of a processing liquid to a lithographic plate, comprising a pair of entry rollers and a pair of exit rollers which guide and feed said lithographic platE along a path through the apparatus, rotatable brush means wetted by the processing liquid located beneath said path in position to brush the under face of said lithographic plate in the same direction as that in which said lithographic plate moves along said path, said lithographic plate being supported between said entry rollers and said exit rollers only by said brush means, and backing means located above said path and including a depending member extending transversely across said path and engaging the upper face of said lithographic plate to urge said lithographic plate into brushing relationship with said rotatable brush means and to engage and deflect, away from the trailing edge of the lithographic plate, a part of the brushing portion of said rotatable brush means which is upstream of the trailing edge of the lithographic plate during the passage of the lithographic plate downstream away from said rotatable brush means.
 2. Apparatus as claimed in claim 1, wherein said backing means comprises a backing plate and the depending member projects from the backing plate towards the brush means.
 3. An apparatus as claimed in claim 2, wherein the depending member comprises a rib normal to the backing plate.
 4. An apparatus as claimed in claim 3, and further comprising an inclined plate having one edge secured to that end of the rib most remote from the backing plate and its opposite edge secured to a part of the backing plate downstream of the rib.
 5. An apparatus as claimed in claim 2, wherein the depending member comprises two oppositely inclined plates having first edges secured together and second edges, opposite to said first edges, secured to the backing plate, the points of attachment of the inclined plates to the backing plate being spaced apart in the direction of said path.
 6. An apparatus as claimed in claim 2, wherein the depending member comprises an arcuate plate secured to said backing plate.
 7. An apparatus as claimed in claim 2, wherein the depending member comprises a roller rotatably mounted on said backing plate.
 8. An apparatus as claimed in claim 1, wherein the brush means is in the form of a cylindrical brush rotatable about an axis and wherein the depending member of the backing member is disposed vertically above the axis.
 9. An apparatus as claimed in claim 8, which includes more than one cylindrical brush rotatable about an axis and more than one depending member, each cylindrical brush being associated with a depending member.
 10. An apparatus as claimed in claim 1, which includes more than one of the rotatable brush means and more than one depending member, each rotatable brush means being associated with a depending member. 